Summary
This appears to be a recent change in expected behavior. Previously ctrl-clicking on a preview opened the page in a new tab. Now the same happens but it also registers as having clicked the preview. The result is two tabs with the same article open. The desired outcome is a new tab open with the ctrl-clicked article and the reader is left in the original window to continue reading the current article.

Steps to reproduce

1. Visit a wiki with Page Previews enabled.
2. Hover over a link to activate a page preview
3. Ctrl or command +click somewhere in the preview

Outcome: Both the current window and a new tab are directed to the target page

Expected behavior: Ctrl+clicking will open the page in the preview in a new tab. The current window will not be affected.

Tested in latest version of Safari and Chrome on the latest version of MacOS.

First reported: https://www.mediawiki.org/wiki/Topic:Ui0q8z2djjkdqapu

Developer notes

git bisect shows this was caused by https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Popups/+/442880/ (T192773)

Some possible ways to fix this behaviour as well as the issue described in T192773

1. revert the patch for T192773 and rethink the approach for that by wrapping the entire popup including image in a link.
2. Use window.open (seems risky as modifier keys may differ by browser)
3. Decline this card or other card
4. Refactor linkClick to take the ev and stopPropagation to the link element/don't open link, if any modifier key held (untested but might work but might have cause other unexpected behaviour)